Thermal receiver and solar thermal power generation device

ABSTRACT

A thermal receiver includes a heat absorption body and a support body. The heat absorption body is made of at least one honeycomb unit having a plurality of flow paths arranged for circulation of a heat medium. The support body supports the heat absorption body and allows circulation of the heat medium. The heat absorption body includes silicon carbide and is supported at a position away from an inner surface of the support body by a predetermined distance.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalApplication No. PCT/JP2011/074520, filed Oct. 25, 2011, which claimspriority to Japanese Patent Application No. 2010-239008, filed Oct. 25,2010. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermal receiver and a solar thermalpower generation device.

2. Discussion of the Background

As a power generation method using the sun, solar thermal powergeneration is known. In the solar thermal power generation, for example,light radiated from the sun is collected using reflecting mirrors or thelike, and a vapor turbine is driven using obtained solar heat, therebygenerating power. In the solar thermal power generation, sincegreenhouse effect gases, such as carbon dioxide, are not generatedduring power generation and heat can be stored, power generation ispossible even under cloudy weather conditions or at night. Therefore,the solar thermal power generation has been paid attention as a futurepromising method of power generation.

The method of the solar thermal power generation can be roughlyclassified into two types, a trough type and a tower type.

The tower-type solar thermal power generation refers to a powergeneration method in which solar light is concentrated and collected ata thermal receiver present in a tower installed at the center portionusing a number of plane mirrors called heliostats, and power isgenerated using the heat. In the case of the tower-type solar thermalpower generation, since solar light collected using several hundred toseveral thousand of several square meter plane mirrors can beconcentrated at one place, the thermal receiver can be heated toapproximately 1000° C. Therefore, the tower-type solar thermal powergeneration has a favorable thermal efficiency.

As the thermal receiver for the tower-type solar thermal powergeneration, U.S. Pat. No. 6,003,508 discloses a receiver in which a heatabsorption body, which is made of silicon carbide, or silicon andsilicon carbide, and has a number of gas flow paths for the circulationof a heat medium, is supported and fixed by a funnel-shaped supportbody.

In the thermal receiver, a heat medium made of air or a gas mixtureincluding the air is circulated through the flow paths in the heatedheat absorption body, whereby the heat medium can obtain heat. In thetower-type solar thermal power generation, water is boiled and vaporizedusing the obtained heat, and a vapor turbine is driven, therebygenerating power.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a thermal receiverincludes a heat absorption body and a support body. The heat absorptionbody is made of at least one honeycomb unit having a plurality of flowpaths arranged for circulation of a heat medium. The support bodysupports the heat absorption body and allows circulation of the heatmedium. The heat absorption body includes silicon carbide and issupported at a position away from an inner surface of the support bodyby a predetermined distance.

According to another aspect of the present invention, a solar thermalpower generation device includes the thermal receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1A is a vertical cross-sectional view schematically illustrating athermal receiver according to a first embodiment of the invention, andFIG. 1B is a cross-sectional view of the thermal receiver cut along theline A-A illustrated in FIG. 1A.

FIG. 2 is a cross-sectional view schematically illustratingcross-sectional area A and cross-sectional area B used for computing anarea proportion of a heat insulating region.

FIG. 3A is a vertical cross-sectional view schematically illustrating athermal receiver according to a second embodiment of the invention, andFIG. 3B is a cross-sectional view of the thermal receiver cut along theline B-B illustrated in FIG. 3A.

FIG. 4A is a vertical cross-sectional view schematically illustrating athermal receiver according to a third embodiment of the invention, andFIG. 4B is a cross-sectional view of the thermal receiver cut along theline C-C illustrated in FIG. 4A.

FIG. 5A is a front view schematically illustrating a receiver array thatconfigures a solar thermal power generation device according to a fourthembodiment of the invention, and FIG. 5B is a cross-sectional view ofthe receiver array cut along the line C-C illustrated in FIG. 5A.

FIG. 6 is an explanatory view schematically illustrating the solarthermal power generation device according to the fourth embodiment ofthe invention.

FIG. 7 illustrates graphs of the temperature changes of samples inExamples 1 to 3 and Comparative example 1 of the invention.

FIG. 8 is a graph illustrating the relationship between the areaproportions of the heat insulating regions and the peak temperatures ofthe samples in Examples 1 to 3 and Comparative example 1 of theinvention.

FIG. 9 illustrates graphs of the temperature changes of samples inExamples 4 to 6 and Comparative example 2 of the invention.

FIG. 10 is a graph illustrating the relationship between the areaproportions of the heat insulating regions and the peak temperatures ofthe samples in Examples 4 to 6 and Comparative example 2 of theinvention.

FIG. 11 illustrates graphs of the temperature changes of samples inExamples 7 to 9 and Comparative example 3 of the invention.

FIG. 12 is a graph illustrating the relationship between the areaproportions of the heat insulating regions and the peak temperatures ofthe samples in Examples 7 to 9 and Comparative example 3 of theinvention.

DESCRIPTION OF THE EMBODIMENTS

That is, according to an embodiment of the invention, there is provideda thermal receiver used in a solar thermal power generation device,including

a heat absorption body made of one or multiple honeycomb units havingmultiple flow paths arranged in parallel for circulation of a heatmedium, and a support body which supports the heat absorption body andallows circulation of the heat medium, in which the heat absorption bodyis configured to include silicon carbide, and is supported apredetermined distance away from an inner surface of the support body.

In the thermal receiver, since the heat absorption body is supported apredetermined distance away from the inner surface of the support body,it is possible to use a space between the heat absorption body and thesupport body as a heat insulating layer, and to effectively prevent heatfrom scattering from the heat absorption body to the support body.

In the thermal receiver, since the heat absorption body is configured toinclude silicon carbide, thermal conductivity is high. In addition,since the heat absorption body is excellent in terms of thermalresistance, cracking and the like do not occur easily, and obtained heatcan be smoothly transferred to the heat medium. In addition, sincesilicon carbide is stable even at 1600° C. in the atmosphere,performances of the heat absorption body are hard to change even inlong-term use.

In a thermal receiver, a holding material can be interposed between theheat absorption body and the support body. In such case, and the holdingmaterial functions as the heat insulating layer. Therefore, it ispossible to effectively prevent heat from scattering from the heatabsorption body to the support body, to firmly hold the heat absorptionbody using the holding material, and to stably use the heat absorptionbody for a long period of time.

In a thermal receiver, the heat absorption body can be firmly supportedand fixed by fixing members provided in the support body. In addition,an air layer can be present between the heat absorption body and thesupport body excluding the fixing members. In such case, the air layerfunctions as the heat insulating layer, and it is possible toeffectively prevent heat from scattering from the heat absorption bodyto the support body.

In a thermal receiver, an inorganic heat insulating member can beinterposed between the heat absorption body and the support body. Insuch case, and the inorganic heat insulating member functions as theheat insulating layer. Therefore, it is possible to effectively preventheat from scattering from the heat absorption body to the support body,to firmly hold the heat absorption body using the inorganic heatinsulating member, and to stably use the heat absorption body for a longperiod of time.

In a thermal receiver, the holding material can be made of analumina-silica fiber, an alumina fiber or a silica fiber. In such case,the holding material has an excellent heat insulating property andthermal resistance. Therefore, the holding material is not fused evenwhen the temperature of the heat absorption body increases toapproximately 1000° C. Therefore, the thermal receiver can hold the heatinsulating property, firmly hold the heat absorption body, and be stablyused for a long period of time.

In a thermal receiver, the thermal receiver can be made of analumina-silica fiber in which a composition ratio between alumina andsilica (alumina/silica) is 60/40 to 80/20. In such case, the holdingmaterial has an excellent heat insulating property and thermalresistance so that the holding material may hold the heat insulatingproperty, and firmly hold the heat absorption body without being fusedeven when the temperature of the heat absorption body increases toapproximately 1000° C.

In a thermal receiver, when a cross-sectional area of a surface parallelto a surface of the heat absorption body, to which solar light isradiated, is indicated by A, and an opening area of the support bodyincluding the surface parallel to the surface to which solar light isradiated is indicated by B, an area proportion of a heat insulatingregion, which is represented by the following formula (1), can be 5% to50%,

Area proportion of the heat insulating region (%)=(B−A)×100/B  (1)

In such case, a layer having the above proportion functions as the heatinsulating layer, and thermal diffusion from the heat absorption bodycan be prevented.

When the area proportion of the heat insulating region is less than 5%,since the proportion of the heat insulating region is too small, it isnot possible to sufficiently prevent thermal diffusion, and, when thearea proportion of the heat insulating region exceeds 50%, the heatinsulating effect barely improves even when the heat insulating regionis further increased.

In a thermal receiver, the heat absorption body can be made of poroussilicon carbide. In such case, the thermal conductivity is high, and theobtained heat can be smoothly transferred to the heat medium.

In a thermal receiver, the heat absorption body can include poroussilicon carbide and silicon that fills up the pores in the poroussilicon carbide. In such case, the heat absorption body becomes a densebody. When the heat absorption body is a dense body, the heat storingproperty of the heat absorption body increases. In addition, since thethermal conductivity of the heat absorption body, which is a dense body,is high, the obtained heat can be smoothly transferred to the heatmedium.

In a thermal receiver, porosity of the porous silicon carbide can be 35%to 60%, an average pore diameter can be 5 μm to 30 μm, and the thermalreceiver can have open pores. In such case, silicon smoothly fills upthe inside of the pores when filling the silicon.

In a thermal receiver, the heat absorption body can be made of densesilica carbide. In such case, the heat storing property of the heatabsorption body increases. In addition, since the heat absorption bodymade of dense silicon carbide has an extremely high thermalconductivity, the obtained heat can be smoothly transferred to the heatmedium.

In a thermal receiver, flow paths can be formed in the heat absorptionbody at 31.0 paths/cm² to 93.0 paths/cm², and a thickness of a wallportion between the flow paths in the heat absorption body can be 0.1 mmto 0.5 mm. In such case, the flow paths in the heat absorption bodyfacilitates the circulation of the heat medium, whereby heat isefficiently transferred to the heat medium from the heat absorptionbody, and, consequently, it is possible to generate power at a highefficiency.

In a solar thermal power generation device according to an embodiment ofthe invention, the above-described thermal receiver is used. In suchcase, the thermal conductivity of the heat absorption body is favorable.Furthermore, since the thermal receiver has the heat insulating layerand does not allow the scattering of heat, it is possible to efficientlyconvert radiated solar light into heat, and to efficiently generatepower.

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

First Embodiment

Hereinafter, a first embodiment, which is an embodiment of the thermalreceiver of the invention, will be described with reference to theaccompanying drawings.

FIG. 1A is a vertical cross-sectional view schematically illustrating athermal receiver according to the first embodiment of the invention, andFIG. 1B is a cross-sectional view of the thermal receiver cut along theline A-A illustrated in FIG. 1A. FIG. 1A is a vertical cross-sectionalview cut in parallel with flow paths in honeycomb units that configure aheat absorption body accommodated in the thermal receiver, and FIG. 1Bis a cross-section perpendicular to the flow paths.

As illustrated in FIGS. 1A and 1B, a thermal receiver 10 according tothe present embodiment of the invention is configured to include a heatabsorption body 11, to which multiple honeycomb units 13 having multipleflow paths 13 b arranged in parallel for the circulation of a heatmedium 14 are adhered through a seal material layer 15 that functions asan adhesive, and a support body 12 which accommodates and supports theheat absorption body 11 and allows the circulation of the heat medium14. In addition, a holding material 17 made of an inorganic fiber isinterposed between the heat absorption body 11 and the support body 12,and the heat absorption body 11 is supported and fixed by the supportbody 12 through the holding material 17. The heat absorption body 11 ismade of one honeycomb unit 13.

The honeycomb unit 13 is made of porous silicon carbide having openpores.

In the thermal receiver 10 according to the embodiment of the invention,the porosity of the porous silicon carbide is desirably 35% to 60%. Whenthe porosity of the porous silicon carbide is less than 35%, since somepores are liable to become closed pores, and it becomes difficult forthe heat medium to intrude into the pores, the thermal conductivitybecomes liable to degrade. On the other hand, when the porosity of theporous silicon carbide exceeds 60%, the strength of the honeycomb unit13 decreases, and the honeycomb unit becomes liable to be broken due tothe repetition of the increase and decrease in the temperature of thehoneycomb unit 13 (thermal history).

Meanwhile, the porosity is a value measured using a mercury intrusionmethod.

The average pore diameter of the porous silicon carbide is desirably 5μm to 30 μm. When the average pore diameter of the porous siliconcarbide is less than 5 μm, the pores in the porous silicon carbide areliable to become closed pores, and it becomes difficult for the heatmedium to intrude into the pores. Therefore, the thermal conductivity ofthe honeycomb unit 13 becomes liable to decrease. On the other hand,when the average pore diameter of the porous silicon carbide exceeds 30μm, the mechanical strength of the porous silicon carbide decreases,and, consequently, the strength of the honeycomb unit 13 also decreases.

In the honeycomb unit 13 according to the embodiment of the invention,when a cross-section perpendicular to the flow paths 13 b is formed, thenumber of the flow paths 13 b per square centimeter is desirably 31.0paths/cm² to 93.0 paths/cm². In a case in which the number of the flowpaths 13 b in the honeycomb unit 13 is less than 31.0 paths/cm², sincethe number of the flow paths 13 b in the honeycomb unit 13 is small, itbecomes difficult for the honeycomb unit 13 to efficiently exchange heatwith the heat medium. On the other hand, when the number of the flowpaths 13 b in the honeycomb unit 13 exceeds 93.0 paths/cm², since thecross-sectional area of a flow path 13 b in the honeycomb unit 13becomes small, it becomes difficult for the heat medium to circulate.

In addition, the thickness of a wall portion between the flow paths inthe honeycomb unit 13 is preferably 0.1 mm to 0.5 mm. When the thicknessof the wall portion in the honeycomb unit 13 is less than 0.1 mm, themechanical strength of the wall portion in the honeycomb unit 13decreases, and the honeycomb unit becomes liable to be broken. On theother hand, when the thickness of the wall portion in the honeycomb unit13 exceeds 0.5 mm, since the wall portion in the honeycomb unit 13becomes too thick, and the circulation amount of the heat medium 14decreases with respect to the area of the honeycomb unit 13, the thermalefficiency degrades.

In the honeycomb unit 13 according to the embodiment of the invention,the porous silicon carbide is used, but a different porous ceramic canbe also used. Examples of the other porous ceramics include nitrideceramics, such as aluminum nitride, silicon nitride and boron nitride;and carbide ceramics, such as silicon carbide, zirconium carbide andtantalum carbide. The above ceramics have a characteristic of having ahigh thermal conductivity.

Meanwhile, in FIG. 1B, the cross-sectional shape of the flow path 13 bin the honeycomb unit 13 is rectangular, but the cross-sectional shapeof the flow path 13 b is not particularly limited, and may be hexagonalor the like. In addition, the cross-sectional figure of the support body12 illustrated in FIG. 1B is rectangular, but is not particularlylimited to be rectangular, and may be hexagonal or the like.

In the embodiment, the heat absorption body 11 is manufactured usingmultiple honeycomb units 13, and the honeycomb units 13 are adhered toeach other using adhesive paste including at least one of inorganicparticles, an inorganic fiber and an inorganic binder as an adhesive.Therefore, the honeycomb units form the heat absorption body 11 which ismade up of multiple honeycomb units 13 and adhesive layers. The adhesivepaste may include an organic binder.

Examples of the inorganic binder included in the adhesive paste includea silica sol, an alumina sol and the like. The inorganic binder may beused solely or in combination of two or more kinds. Among the inorganicbinders, a silica sol is desirable.

In addition, the lower limit of the content of the inorganic binder isdesirably 1 weight %, and more desirably 5 weight % in terms of solidcontent. On the other hand, the upper limit of the content of theinorganic binder is desirably 30 weight %, and more desirably 15 weight% in terms of solid content. When the content of the inorganic binder isless than 1 weight % in terms of solid content, the adhesion strength isliable to decrease. On the other hand, when the content of the inorganicbinder exceeds 30 weight % in terms of solid content, the thermalconductivity of the adhesive layer is liable to decrease.

Examples of the organic binder included in the adhesive paste includepolyvinyl alcohols, methyl cellulose, ethyl cellulose, carboxymethylcellulose and the like. The organic binder may be used solely or incombination of two or more kinds. Among the organic binders,carboxymethyl cellulose is desirable.

The lower limit of the content of the organic binder is desirably 0.1weight %, and more desirably 0.4 weight % in terms of solid content. Onthe other hand, the upper limit of the content of the organic binder isdesirably 5.0 weight %, and more desirably 1.0 weight % in terms ofsolid content. When the content of the organic binder is less than 0.1weight % in terms of solid content, the adhesive layer becomes liable tomigrate. On the other hand, when the content of the organic binderexceeds 5.0 weight % in terms of solid content, the adhesive forcebetween the adhesive layer and the honeycomb unit is liable to decrease.

Examples of the inorganic fiber included in the adhesive paste includeceramic fibers, such as silica-alumina, mullite, alumina, and silica;and the like. The inorganic fiber may be used solely or in combinationof two or more kinds. Among the inorganic fibers, an alumina fiber isdesirable.

The lower limit of the content of the inorganic fiber is desirably 10weight %, and more desirably 20 weight %. On the other hand, the upperlimit of the content of the inorganic fiber is desirably 70 weight %,and more desirably 40 weight %. When the content of the inorganic fiberis less than 10 weight %, the elasticity of the adhesive layer becomesliable to decrease. On the other hand, when the content of the inorganicfiber exceeds 70 weight %, the thermal conductivity of the adhesivelayer is liable to decrease, and the effect as the elastic body becomesliable to degrade.

Examples of the inorganic particles included in the adhesive pasteinclude carbides, nitrides and the like. Specific examples includeinorganic powder made of silicon carbide, silicon nitride or boronnitride, and the like. The inorganic particles may be used solely or incombination of two or more kinds. Among the inorganic particles, siliconcarbide having excellent thermal conductivity is desirable.

The lower limit of the content of the inorganic particles is desirably 3weight %, more desirably 10 weight %, and still more desirably 20 weight%. On the other hand, the upper limit of the content of the inorganicparticles is desirably 80 weight %, and more desirably 40 weight %. Whenthe content of the inorganic particles is less than 3 weight %, thethermal conductivity of the adhesive layer becomes liable to decrease.On the other hand, when the content of the inorganic particles exceeds80 weight %, the adhesion strength is liable to decrease in a case inwhich the adhesive layer is exposed to a high temperature.

The organic binder included in the adhesive layer is decomposed andeliminated when the temperature of the honeycomb unit 13 increases;however, since the inorganic particles and the like are included in theadhesive layer, it is possible to maintain a sufficient adhesive force.

In the embodiment, the adhesive layer desirably includes the inorganicparticles, the inorganic fiber and the inorganic binder (the solidcontent of the inorganic binder). Furthermore, the adhesive layer ismore desirably formed using adhesive paste including the inorganicparticles, the inorganic fiber, the organic binder and the inorganicbinder.

The support body 12 has a rectangular front cross-sectional shape asillustrated in FIG. 1B, but has an overall shape of a funnel shape. Thatis, the cross-section of an enlarged portion 12 a, in which the heatabsorption body 11 is accommodated and into which the heat medium 14flows (the cross-section in parallel to the surface of the heatabsorption body 11 which receives solar light), has a large area;however, as the cross section is shifted in an exit direction of theheat medium 14, the area of the cross-section gradually decreases, andthe cross-sectional area becomes a substantially constant area at anexit 12 b for the heat medium.

The material of the support body 12 is not particularly limited;however, since the heat absorption body 11 reaches approximately 1000°C., the material of the support body 12 needs to have thermalresistance, and therefore a metal or a ceramic is preferable.

Examples of the metal material include iron, nickel, chromium, aluminum,tungsten, molybdenum, titanium, lead, copper, zinc, alloys thereof, andthe like. In addition, examples of the ceramic include carbide ceramics,such as aluminum nitride, silicon nitride, boron nitride and titaniumnitride; oxide ceramics, such as silica, alumina, mullite and zirconia;and the like. Examples of additional materials of the support body 12include complexes of a metal and a nitride ceramic, complexes of a metaland a carbide ceramic, and the like. The material of the support body ispreferably a ceramic, such as alumina or silicon carbide, in terms ofthermal resistance.

In the thermal receiver 10 according to the embodiment of the invention,the holding material 17 is interposed between the heat absorption body11 and the support body 12.

The holding material 17 is configured of a mat, which is made of aninorganic fiber and has a rectangular shape in the planar view, or bylaminating multiple mats. When the holding material 17 is accommodatedin the support body 12 in a state in which the holding material 17 iswound around the side surfaces of the heat absorption body 11, it ispossible to support and fix the heat absorption body 11 in the supportbody 12. Therefore, it is possible to prevent the heat stored in theheat absorption body 11 from diffusing.

Regarding the proportion of the cross-sectional area of the heatinsulating region, which is made of the holding material 17, in thecross-sectional opening area of the support body 12 (hereinafter alsoreferred to as “area proportion of the heat insulating region”), whenthe cross-sectional area of a surface parallel to the surface of theheat absorption body 11, to which solar light is radiated, is indicatedby A, and the opening area of the support body 12 including the surfaceparallel to the surface to which solar light is radiated is indicated byB, the area proportion of the heat insulating region, which isrepresented by the following formula (1), is desirably 5% to 50%,

Area proportion of the heat insulating region (%)=(B−A)×100/B  (1)

FIG. 2 is a cross-sectional view schematically illustrating thecross-sectional area A and the cross-sectional area B, which are usedfor computing the area proportion of the heat insulating region.

In FIG. 2, the cross-sectional view illustrated in FIG. 1B is used, theoutermost outline illustrated in the drawing is the outside outline ofthe support body 12, and the inside portion of the outline B inside theoutermost outline indicates the opening area B of the support body 12.In addition, the outline A inside the opening area indicates thecross-sectional area A of the heat absorption body 11. Therefore, thehatching portion illustrates the cross-sectional area of the heatinsulating region (B-A), the area proportion of the heat insulatingregion becomes the percentage of the cross-sectional area of the heatinsulating region (B-A) with respect to the opening area B of thesupport body 12, and forms the formula (1).

When the area proportion of the heat insulating region is less than 5%,since the proportion of the heat insulating region of the holdingmaterial is too small, it is not possible to sufficiently prevent thediffusion of the heat medium. On the other hand, when the areaproportion of the heat insulating region exceeds 50%, the heatinsulating effect barely improves even when the area proportion isfurther increased.

It is considered that the above desirable range of the area proportionof the heat insulating region can be similarly applied to a case inwhich a different material is used as the heat insulating material or acase in which the heat insulating area is made up of an air layer andfixing members in addition to a case in which the holding material 17 isused as the heat insulating material. Meanwhile, the heat absorptionbody 11 is desirably disposed so that the intervals between the heatabsorption body 11 and the support body 12, which are present above andbelow the heat absorption body 11 and on the right and left sides of theheat absorption body, become the same.

The inorganic fiber that configures the holding material 17 is notparticularly limited, and may be an alumina-silica fiber. Examplesthereof include an alumina fiber, a silica fiber, Rockwell, and thelike. The inorganic fiber may be changed depending on thecharacteristics and the like required for the holding material, such asthermal resistance or wind erosion resistance. In a case in which analumina-silica fiber is used as the inorganic fiber, an alumina-silicafiber having a composition ratio between alumina and silica of, forexample, 60:40 to 80:20 is desirably used.

A needle punching treatment is desirably carried out on the holdingmaterial 17. When a needle punching treatment is carried out on theholding material, the constituent material, such as the inorganic fiber,of the mat that configures the holding material is not easily separated,and can be made into a single well-organized mat shape. In addition,when a needle punching treatment is carried out on the holding materialin the width direction, which is perpendicular to the longitudinaldirection, fold lines are generated in the width direction of the matthat configures the holding material at portions on which the needlepunching treatment has been carried out. Therefore, it becomes easy towind the holding material when the holding material is wound around theheat absorption body.

In addition, as the holding material 17, a material obtained byimpregnating an organic binder including an acryl-based resin and thelike in the mat that configures the holding material, and compressivelydrying the mat so as to have a thin thickness may be used. When thereflected light of solar light is radiated on the heat absorption body11 after the holding material 17 is wound around the heat absorptionbody 11, and pushed into the support body 12 so as to fit the heatabsorption body 11 into the support body 12, the temperature of the heatabsorption body 11 increases to approximately 1000° C. Therefore, theorganic binder is decomposed and eliminated, and the compression stateformed by the organic binder in the mat which configures the holdingmaterial 17 is released so that it becomes easy for the heat absorptionbody 11 to be firmly supported and fixed by the support body 12.

Hereinafter, a method for manufacturing the thermal receiver accordingto the embodiment will be described.

First, the porous silicon carbide that configures the honeycomb unit ismanufactured.

When manufacturing the porous silicon carbide, silicon carbide powderhaving different average particle diameters, which is a raw material, anorganic binder, a plasticizer, a lubricant, water and the like aremixed, thereby preparing a wet mixture.

Subsequently, a molding process, in which the wet mixture is injectedinto an extrusion molding machine, and is extrusion-molded, is carriedout, thereby manufacturing a quadratic prismatic compact of thehoneycomb unit having multiple flow paths formed in the longitudinaldirection.

Next, a cutting process, in which both ends of the compact of thehoneycomb unit are cut using a cutting apparatus, is carried out so asto cut the compact of the honeycomb unit into a predetermined length,and the cut compact of the honeycomb unit is dried using a dryingmachine.

Next, a defatting process, in which the organic substances in thecompact of the honeycomb unit are heated in a defatting furnace, iscarried out, the compact is transported to a firing furnace, and afiring process is carried out, thereby manufacturing the honeycomb unit(porous silicon carbide).

When multiple honeycomb units are adhered to each other, the adhesivepaste is coated on the side surfaces (surfaces on which the flow pathsare not formed) of the honeycomb units, the honeycomb units are adheredto each other, and then dried, thereby forming the adhesive layer. Whensolar thermal power generation is carried out, since the heat absorptionbody 11 is irradiated with solar light so as to reach a temperature ofapproximately 1000° C., moisture and the like in the adhesive layer arevaporized, and the organic binder is decomposed and eliminated. However,the inorganic fiber and the inorganic particles are joined using thesolid content of the inorganic binder included in the adhesive layer,which forms a strong adhesive layer.

The support body can be manufactured using a method which has been thusfar used. When manufacturing the support body made of a ceramic, thesupport body can be manufactured by carrying out the defatting processand the firing process after the pressing, injection molding, castingand the like of a mixture including ceramic powder, the organic binderand the like.

When assembling the thermal receiver 10, the holding material 17 iswound around the heat absorption body 11 manufactured using the abovemethod, and pushed into the support body 12 so as to be fixed, therebyassembling the thermal receiver 10.

Hereinafter, the actions and effects of the thermal receiver of theembodiment will be listed.

(1) Since the thermal receiver of the embodiment has the heat absorptionbody including the honeycomb units made of porous silicon carbide, thethermal conductivity is high, and the obtained heat can be smoothlytransferred to the heat medium, such as air. In addition, since siliconcarbide that configures the honeycomb unit is stable in the air even at1600° C., the performances are not easily changed even in long-term use.

(2) In the thermal receiver of the embodiment, the holding material isinterposed between the heat absorption body and the support body, andthe heat absorption body can be firmly held using the holding material.In addition, since the holding material functions as the heat insulatinglayer, it is possible to effectively prevent heat from scattering fromthe heat absorption body to the support body.

(3) In the thermal receiver of the embodiment, the heat absorption bodyis configured of multiple honeycomb units adhered through the adhesivelayer formed on the side surfaces, for which the adhesive paste is used.Therefore, the honeycomb units are firmly adhered to each other. Inaddition, since the adhesive layer has thermal resistance, it ispossible to reliably prevent some of the honeycomb units from dropping,which may be caused by a force exerting in the flowing direction of theheat medium which flows through the flow paths for the heat medium.

(4) In the thermal receiver of the embodiment, in the heat absorptionbody made up of the honeycomb units, the flow paths are formed at 31.0paths/cm² to 93.0 paths/cm², the thickness of the wall portion betweenthe flow paths in the honeycomb unit is 0.1 mm to 0.5 mm, the porosityof the porous silicon carbide is 35% to 60%, and the average porediameter is 5 μm to 30 μm. Therefore, it becomes easy for the silicon tofill up the pores in the porous silicon carbide. The heat medium flowsthrough the flow paths in the honeycomb unit, and therefore heat isefficiently transferred from the dense heat absorption body to the heatmedium. As a result, in the solar thermal power generation device, inwhich the thermal receiver is used, power can be generated at a highefficiency.

EXAMPLES

Hereinafter, examples, in which the first embodiment of the invention isdisclosed more specifically, will be described, but the invention is notlimited to the examples.

Example 1

(Process for Manufacturing a Fired Compact of the Honeycomb Unit)

Coarse powder of silicon carbide having an average particle diameter of22 μm (52.8 weight %) and fine powder of silicon carbide having anaverage particle diameter of 0.5 μm (22.6 weight %) were mixed, an acrylresin (2.1 weight %), an organic binder (methyl cellulose, 4.6 weight%), a lubricant (UNIROOF manufactured by NOF Corporation, 2.8 weight %),glycerin (1.3 weight %) and water (13.8 weight %) were added to theobtained mixture, and the components were kneaded, thereby obtaining awet mixture. An extrusion molding process, in which the obtained wetmixture was extrusion-molded, was carried out, thereby manufacturing aquadratic prismatic compact of the honeycomb unit.

Next, the raw compact of the honeycomb unit was dried using a microwavedrying machine, thereby producing a dried compact of the honeycomb unit.

A defatting process, in which the dried compact of the honeycomb unitwas defatted at 400° C., was carried out, a firing process was carriedout under conditions of an argon atmosphere, a normal pressure, 2200° C.and 3 hours, thereby manufacturing a honeycomb unit 13 made of siliconcarbide. The porosity of the obtained honeycomb unit 13 was 42%, theaverage pore diameter was 11 μm, the size was 34.3 mm×34.3 mm×45 mm, thenumber of cells (cell density) was 50 cells/cm², and the thickness ofthe cell wall was 0.25 mm (10 mil).

(Adhering Process)

Next, a thermal resistant double-sided tape was adhered to the adhesionsurface of the obtained honeycomb unit 13 made of porous siliconcarbide, and a total of 16 (4×4) honeycomb units 13 were adhered to eachother through the thermal resistant double-sided tape, thereby producingthe heat absorption body 11.

Next, the holding material 17, which was a sheet-like inorganic fibermade of Al₂O₃ and SiO₂ at a composition ratio of 72:28 (weight ratio),and had an average fiber diameter of the inorganic fiber of 5.1 μm(average fiber length 60 mm), a bulk density of 0.15 g/cm³ and a fiberdensity of 1400 g/m², was wound around the obtained heat absorption body11 so that the thickness became 21 mm, thereby producing a sample fortemperature measurement.

A thermal receiver can be produced by inserting and fixing the samplefor temperature measurement in the support body 12.

At this time, the dimensions of the heat absorption body 11 become 137.2mm in height and 137.2 mm in width. In the present example, since the 21mm-thick holding material 17 is wound around the heat absorption body11, when the area proportion of the heat insulating region is computedwith an assumption that the support body 12 is disposed around theholding material 17, the following is obtained.

[Cross-sectional area B(179.2×179.2)−cross-sectional areaA(137.2×137.2)]×100/cross-sectional area B(179.2×179.2)=41.4(%)

That is, the area proportion of the heat insulating region becomes41.4%.

Example 2

A sample for temperature measurement was produced in the same manner asin Example 1 except that the thickness of the holding material 17 wasset to 14 mm. When the area proportion of the heat insulating region iscomputed in the same manner as in Example 1 for the sample, thefollowing is obtained.

[Cross-sectional area B(165.2×165.2)−cross-sectional areaA(137.2×137.2)]×100/cross-sectional area B(165.2×165.2)=31.0(%)

That is, the area proportion of the heat insulating region becomes31.0%.

Example 3

A sample for temperature measurement was produced in the same manner asin Example 1 except that the thickness of the holding material 17 wasset to 7 mm. When the area proportion of the heat insulating region iscomputed in the same manner as in Example 1 for the sample, thefollowing is obtained.

[Cross-sectional area B(151.2×151.2)−cross-sectional areaA(137.2×137.2)]×100/cross-sectional area B(151.2×151.2)=17.7(%)

That is, the area proportion of the heat insulating region becomes17.7%.

Example 4

The honeycomb unit 13 was manufactured in the same manner as in Example1, and a total of 9 (3×3) honeycomb units 13 were adhered using athermal resistant double-sided tape, thereby producing the heatabsorption body 11.

Next, the same holding material 17 as the holding material 17 used inExample 1 was wound around the obtained heat absorption body 11 so thatthe thickness became 21 mm, thereby producing a sample for temperaturemeasurement. At this time, the dimensions of the heat absorption body 11become 102.9 mm in height and 102.9 mm in width. In the present example,since the 21 mm-thick holding material 17 is wound around the heatabsorption body 11, when the area proportion of the heat insulatingregion is computed with an assumption that the support body 12 isdisposed around the holding material 17, the following is obtained.

[Cross-sectional area B(144.9×144.9)−cross-sectional areaA(102.9×102.9)]×100/cross-sectional area B(144.9×144.9)=49.6(%)

That is, the area proportion of the heat insulating region becomes49.6%.

Example 5

A sample for temperature measurement was produced in the same manner asin Example 4 except that the thickness of the holding material 17 wasset to 14 mm. When the area proportion of the heat insulating region iscomputed in the same manner as in Example 4 for the sample, thefollowing is obtained.

[Cross-sectional area B(130.9×130.9)−cross-sectional areaA(102.9×102.9)]×100/cross-sectional area B(130.9×130.9)=38.2(%)

That is, the area proportion of the heat insulating region becomes38.2%.

Example 6

A sample for temperature measurement was produced in the same manner asin Example 4 except that the thickness of the holding material 17 wasset to 7 mm. When the area proportion of the heat insulating region iscomputed in the same manner as in Example 4 for the sample, thefollowing is obtained.

[Cross-sectional area B(116.9×116.9)−cross-sectional areaA(102.9×102.9)]×100/cross-sectional area B(116.9×116.9)=22.5(%)

That is, the area proportion of the heat insulating region becomes22.5%.

Example 7

The honeycomb unit 13 was manufactured in the same manner as in Example1, and a total of 4 (2×2) honeycomb units 13 were adhered using athermal resistant double-sided tape, thereby producing the heatabsorption body 11.

Next, the same holding material 17 as the holding material 17 used inExample 1 was wound around the obtained heat absorption body 11 so thatthe thickness became 21 mm, thereby producing a sample for temperaturemeasurement. At this time, the dimensions of the heat absorption body 11become 68.6 mm in height and 68.6 mm in width. In the present example,since the 21 mm-thick holding material 17 is wound around the heatabsorption body 11, when the area proportion of the heat insulatingregion is computed with an assumption that the support body 12 isdisposed around the holding material 17, the following is obtained.

[Cross-sectional area B(110.6×110.6)−cross-sectional areaA(68.6×68.6)]×100/cross-sectional area B(110.6×110.6)=61.5(%)

That is, the area proportion of the heat insulating region becomes61.5%.

Example 8

A sample for temperature measurement was produced in the same manner asin Example 7 except that the thickness of the holding material 17 wasset to 14 mm. When the area proportion of the heat insulating region iscomputed in the same manner as in Example 7 for the sample, thefollowing is obtained.

[Cross-sectional area B(96.9×96.9)−cross-sectional areaA(68.6×68.6)×100/cross-sectional area B(96.9×96.9)=49.6(%)

That is, the area proportion of the heat insulating region becomes49.6%.

Example 9

A sample for temperature measurement was produced in the same manner asin Example 7 except that the thickness of the holding material 17 wasset to 7 mm. When the area proportion of the heat insulating region iscomputed in the same manner as in Example 7 for the sample, thefollowing is obtained.

[Cross-sectional area B(82.6×82.6)−cross-sectional areaA(68.6×68.6)×100/cross-sectional area B(82.6×82.6)=31.0(%)

That is, the area proportion of the heat insulating region becomes31.0%.

Comparative Example 1

A sample for temperature measurement was manufactured in the same manneras in Example 1 except that the holding material 17 was not wound aroundthe heat absorption body 11. The area proportion of the heat insulatingregion of the present comparative examples is 0%.

Comparative Example 2

A sample for temperature measurement was manufactured in the same manneras in Example 4 except that the holding material 17 was not wound aroundthe heat absorption body 11. The area proportion of the heat insulatingregion of the present comparative examples is 0%.

Comparative Example 3

A sample for temperature measurement was manufactured in the same manneras in Example 7 except that the holding material 17 was not wound aroundthe heat absorption body 11. The area proportion of the heat insulatingregion of the present comparative examples is 0%.

(Evaluation of the Samples)

The samples for temperature measurement of Examples 1 to 9 andComparative examples 1 to 3 (hereinafter also referred to simply assamples) were irradiated for 30 minutes using a spot photographing lampRPS-500WB (100 V, 150 W) manufactured by Panasonic Corporation at adistance of 100 mm from the surfaces of the samples. The temperatures ofthe samples were measured using a thermocouple directly fitted in thesample every 10 seconds from the beginning of the irradiation to 30minutes after the end of the irradiation.

FIG. 7 illustrates graphs of the temperature changes of the samples inExamples 1 to 3 and Comparative example 1 of the invention, FIG. 9illustrates graphs of the temperature changes of the samples in Examples4 to 6 and Comparative example 2 of the invention, and FIG. 11illustrates graphs of the temperature changes of the samples in Examples7 to 9 and Comparative example 3 of the invention. In the respectivegraphs in FIGS. 7, 9 and 11, the vertical axis indicates the temperature(° C.), and the transverse axis indicates the elapsed time (seconds). Inaddition, FIG. 8 is a graph illustrating the relationship between thearea proportions of the heat insulating regions and the peaktemperatures of the samples in Examples 1 to 3 and Comparative example 1of the invention, FIG. 10 is a graph illustrating the relationshipbetween the area proportions of the heat insulating regions and the peaktemperatures of the samples in Examples 4 to 6 and Comparative example 2of the invention, and FIG. 12 is a graph illustrating the relationshipbetween the area proportions of the heat insulating regions and the peaktemperatures of the samples in Examples 7 to 9 and Comparative example 3of the invention. In the respective graphs in FIGS. 8, 10 and 12, thevertical axis indicates the peak temperature (° C.), and the transverseaxis indicates the area proportion of the heat insulating region (%).Furthermore, the temperature measurement results of the respectiveexamples and the respective comparative examples are described inTable 1. Table 1 describes the peak temperatures and temperatures 30minutes after the end of the irradiation of the lamp of the samplesaccording to the respective examples and the respective comparativeexamples.

TABLE 1 Thick- Number ness Area of of proportion Temperature honey-holding of heat Peak after 30 comb material insulating temperatureminutes units (mm) region (%) (° C.) (° C.) Example 1 16 21 41.4 128.837.5 Example 2 16 14 31.0 126.4 39.3 Example 3 16 7 17.7 118.0 34.4Comparative 16 0 0 99.8 31.1 example 1 Example 4 9 21 49.6 107.0 30.2Example 5 9 14 38.2 106.5 30.0 Example 6 9 7 22.5 99.8 29.0 Comparative9 0 0 76.0 22.2 example 2 Example 7 4 21 61.5 107.1 27.5 Example 8 4 1449.6 108.8 27.0 Example 9 4 7 31.0 97.1 24.0 Comparative 4 0 0 70.0 21.5example 3

As is evident from the results described in FIGS. 7 to 12 and Table 1,it is found that, since the holding material 17 was wound around theperipheries in the samples according to Examples 1 to 9, compared to thesamples, in which the holding material 17 is not formed on theperipheries, as in Comparative examples 1 to 3, heat is not easilyscattered, and the temperature is easily increased. In addition, it isfound that, as the area proportion of the heat insulating regionincreases and the thickness of the holding material 17 increases, theheat insulating property improves; however, when the area proportion ofthe heat insulating region exceeds 50%, the heat insulating performancebecomes substantially constant, and barely changes. Since the area ofthe heat absorption body 11 is preferably as wide as possible, when therelationship between the thickness and the heat insulating efficiency istaken into account, the area proportion of the heat insulating region isconsidered to be preferably 50% or less.

Second Embodiment

Hereinafter, a second embodiment, which is an embodiment of the thermalreceiver of the invention, will be described with reference to theaccompanying drawings.

FIG. 3A is a vertical cross-sectional view schematically illustrating athermal receiver according to the second embodiment of the invention,and FIG. 3B is a cross-sectional view of the thermal receiver cut alongthe line B-B illustrated in FIG. 3A.

As illustrated in FIGS. 3A and 3B, a thermal receiver 40 according tothe second embodiment of the invention is configured to include the heatabsorption body 11, to which multiple honeycomb units 13 having multipleflow paths 13 b arranged in parallel for the circulation of the heatmedium 14 are adhered through an adhesive layer formed of silicon 45that functions as adhesive paste, and the support body 12 whichaccommodates and supports the heat absorption body 11 and allows thecirculation of the heat medium 14. In addition, the holding material 17made of an inorganic fiber is interposed between the heat absorptionbody 11 and the support body 12, and the heat absorption body 11 issupported and fixed by the support body 12 through the holding material17.

The honeycomb unit 13 is made of porous silicon carbide having openpores and the silicon 45 that fills up the open pores in the poroussilicon carbide.

In the thermal receiver 40 according to the embodiment of the invention,the porosity of the honeycomb unit 13 is desirably 35% to 60%. When theporosity of the honeycomb unit 13 is less than 35%, some pores in theporous silicon carbide that configures the honeycomb unit 13 becomeclosed pores, and it becomes difficult to fill the entire pores in thehoneycomb unit 13 with the silicon 15. On the other hand, when theporosity of the honeycomb unit 13 exceeds 60%, the strength of thehoneycomb unit 13 decreases, and the honeycomb unit becomes liable to bebroken due to the repetition of the increase and decrease in thetemperature of the honeycomb unit 13 (thermal history).

The average pore diameter of the porous silicon carbide is desirably 5μm to 30 μm. When the average pore diameter of the porous siliconcarbide is less than 5 μm, the pores in the porous silicon carbide areliable to become closed pores, and it becomes difficult to fill thesilicon. On the other hand, when the average pore diameter of the poroussilicon carbide exceeds 30 μm, the mechanical strength of the poroussilicon carbide that configures the honeycomb unit 13 decreases.

The silicon filling up the open pores in the porous silicon carbide thatconfigures the honeycomb unit 13 is preferably impregnated in 15 partsby weight to 50 parts by weight with respect to 100 parts by weight ofthe porous silicon carbide. When the silicon is impregnated in theporous silicon carbide in the above range, the open pores in the poroussilicon carbide are filled with the silicon, and the honeycomb unitbecomes a dense body.

Similarly to in the first embodiment, the number of the flow paths 13 bper square centimeter in the honeycomb unit 13 according to the secondembodiment of the invention is desirably 31.0 paths/cm² to 93.0paths/cm².

In addition, the thickness of the wall portion between the flow paths isalso preferably 0.1 mm to 0.5 mm, similarly to in the case of the firstembodiment.

In the honeycomb unit 13 according to the embodiment of the invention,the porous silicon carbide is used as a porous ceramic for fillingsilicon, but it is also possible to use a different porous ceramic.Examples of the different porous ceramic include nitride ceramics, suchas aluminum nitride, silicon nitride and boron nitride; and carbideceramics, such as silicon carbide, zirconium carbide and tantalumcarbide. The above ceramics have a high thermal conductivity.

In a case in which the heat absorption body 11 is manufactured usingmultiple honeycomb units 13, it is possible to produce the heatabsorption body 11 by adhering the honeycomb units 13 using the silicon45, which is the same material as the silicon filling up the inside ofthe porous silicon carbide that configures the honeycomb unit 13, as anadhesive.

The support body 12 is configured in the same manner as in the case ofthe first embodiment.

In the thermal receiver 40 according to the embodiment of the invention,the holding material 17 is interposed between the heat absorption body11 and the support body 12, but the holding material 17 is alsoconfigured in the same manner as in the case of the first embodiment.

Hereinafter, a method for manufacturing the thermal receiver accordingto the second embodiment of the invention will be described.

First, the porous silicon carbide that configures the honeycomb unit ismanufactured. The porous silicon carbide can be manufactured in the samemanner as in the case of the first embodiment.

Subsequently, a metal impregnation process, in which a metal isimpregnated into the fired compact of the honeycomb unit, is carriedout. In a case in which silicon is impregnated into the fired compact ofthe honeycomb unit, for example, a carbon material is preferablyimpregnated into the fired compact of the honeycomb unit in advance.Examples of the carbon material include a variety of organic substances,such as furfural resins, phenol resins, lignin sulfonate, polyvinylalcohols, cornstarch, molasses, coal tar pitch and alginate. Meanwhile,a pyrolytic carbon, such as carbon black or acetylene black, can be alsoused in the same manner.

The reason for impregnating the carbon substance into the fired compactof the honeycomb unit in advance is that, since a new silicon carbidefilm is formed on the surfaces of the open pores in the fired compact ofthe honeycomb unit, the bond between the fused silicon and the firedcompact of the honeycomb unit becomes strong. In addition, the reason isthat the strength of the fired compact of the honeycomb unit alsobecomes strong through the impregnation of the honeycomb unit into thefired compact.

In addition, examples of a method for filling the silicon into the openpores in the fired compact of the honeycomb unit include a method inwhich the silicon is heated and fused so as to be absorbed and fill upthe open pores in the fired compact of the honeycomb unit. In this case,silicon having a lump, powder or particle form is placed on the topsurface or bottom surface (side surfaces excluding the end surfaces) ofthe fired compact of the honeycomb unit, the silicon is melted at 1450°C. or more under a vacuum condition, and the silicon fills up the openpores in the fired compact of the honeycomb unit. The impregnation rateof the silicon in the fired compact of the honeycomb unit can becontrolled by changing the orientation of the honeycomb unit, on whichthe silicon is placed, and repeating the above operation, and/orchanging the weight of the silicon being placed.

It is also possible to apply a method in which finely powdered siliconis dispersed in a liquid of a dispersion medium, the liquid of adispersion medium is impregnated in the fired compact of the honeycombunit, dried, and then heated to the fusion temperature or more of thesilicon.

In addition, the metal impregnation process on the fired compact of thehoneycomb unit may be carried out on the compact of the honeycomb unit(that is, the honeycomb unit before the firing process). When the abovemethod is used, it is possible to achieve power saving, and to suppressthe manufacturing costs.

The above method enables the obtainment of a fired compact of thehoneycomb unit filled with the silicon. Meanwhile, the fired compact ofthe honeycomb unit filled with the silicon is called a honeycomb unit.The honeycomb unit can be used as the heat absorption body as it is;however, when multiple honeycomb units are adhered to each other usingthe adhesive paste so as to be used as the heat absorption body, thefollowing method can be used.

That is, when the silicon is used as the adhesive paste, and multiplehoneycomb units are adhered to each other through a silicon layer, thesilicon fills up and is adhered to the porous silicon carbide (honeycombunit) at the same time. In this case, it is possible to use, forexample, a method in which multiple fired compacts of the honeycombunits, in which fine powder-form silicon has been impregnated, areassembled into a shape of the heat absorption body using predeterminedfixing devices and the like, and then heated.

In a case in which the fired compacts of the honeycomb units, in whichsilicon fine powder has not been impregnated, are used, it is possibleto use a method in which multiple fired compacts are assembled, then,silicon is placed on the top surface, bottom surface and the like (sidesurfaces excluding end surfaces) of the fired compacts of the honeycombunits in the vacuum, and heated. The fired compact body of the honeycombunits may be adhered to each other by coating a slurry form of siliconpowder on the side surfaces of the fired compacts of the honeycombunits, and heating the fired compacts in a state in which two firedcompacts of the honeycomb units are in contact with each other throughthe coated surface. Multiple honeycomb units can be joined by carryingout the above operation repeatedly.

Even in a case in which any of the above methods is used, the siliconfills up the open pores in the honeycomb unit (porous silicon carbide),and the silicon spreads into the space between the side surfaces of thehoneycomb units so as to form the adhesive layer, whereby the firedcompacts of the honeycomb units can be adhered to each other through thesilicon. The support body can also be manufactured in the same manner asin the case of the first embodiment.

When assembling the thermal receiver 40, the holding material 17 iswound around the heat absorption body 11 manufactured using the abovemethod, is pushed into and fixed by the support body 12, whereby thethermal receiver 40 can be assembled.

Hereinafter, the actions and effects of the thermal receiver of theembodiment will be listed.

The embodiment does not only exhibit the actions and effects of (2) and(4) of the first embodiment, but also exhibits the following effect.

(5) In the thermal receiver of the embodiment, since the honeycomb unitis configured by including the porous silicon carbide and the siliconthat fills up the open pores in the porous silicon carbide, thehoneycomb unit becomes a dense body. In addition, since the honeycombunit is a dense body, the thermal capacity of the honeycomb unit becomeslarge, and the heat-storing property of the heat absorption bodyincreases. In addition, since the thermal conductivity of the honeycombunit increases, the obtained heat can be smoothly transferred to theheat medium, such as the air.

Third Embodiment

Hereinafter, a third embodiment, which is an embodiment of the thermalreceiver of the invention, will be described.

The thermal receiver according to the present embodiment is configuredin the same manner as in the thermal receiver according to the firstembodiment except that the heat absorption body is supported by fixingmembers provided in the support body, and an air layer is presentbetween the heat absorption body and the support body excluding thefixing members. Therefore, in the following description, a method forfixing the heat absorption body using the fixing members provided in thesupport body will be described.

FIG. 4A is a cross-sectional view schematically illustrating the thermalreceiver according to the third embodiment of the invention, and FIG. 4Bis a cross-sectional view of the thermal receiver cut along the line C-Cillustrated in FIG. 3A.

As illustrated in FIGS. 4A and 4B, in a thermal receiver 50 according tothe third embodiment of the invention, the heat absorption body 11accommodated in the support body 12 is supported and fixed by bolts 18,which are fixing members.

That is, multiple screw holes 12 c for screwing the bolts 18, which aresubstantially columnar fixing members, are formed in the support body12. In addition, multiple bolts 18 are screwed into the screw holes 12c, and the heat absorption body 11 is fixed using the multiple bolts 18.

Although not shown, an elastic fixing auxiliary member having apredetermined thickness may be interposed between the bolts 18 and theheat absorption body 11. The fixing auxiliary member can be manufacturedusing, for example, the inorganic fiber, the inorganic binder and thelike. The heat absorption body 11 can be firmly supported and fixed bythe support body 12 using the elastic fixing auxiliary member.

In the embodiment, the bolts 18 are used as the fixing members, but thefixing members are not limited to the bolts, and any members can be usedas long as screw holes can be opened, and screws can be screwed in. Inaddition, the material is preferably a thermal resistant metal materialor ceramic. Examples of the thermal resistant metal material includeiron, nickel, chromium, aluminum, tungsten, molybdenum, titanium, lead,copper, zinc, alloys of the above metals, and the like. In addition,examples of the ceramic include nitride ceramics, such as aluminumnitride, silicon nitride, boron nitride and titanium nitride; carbideceramics, such as zirconium carbide, titanium carbide, tantalum carbideand tungsten carbide; oxide ceramics, such as silica, alumina, mulliteand zirconia; and the like.

In the embodiment, the heat absorption body 11 is fixed using multiplebolts 18, the air layer is present in portions other than the portionfixed by the bolts 18, and, when the heat medium 14 is suctioned, theair layer portion between the heat absorption body 11 and the supportbody 12 is also suctioned, thereby generating the flow of apredetermined flow amount of the heat medium 14. Therefore, the layer ofthe flowing heat medium 14 functions as the heat insulating layer(heat-retention layer), and it is possible to effectively prevent heatfrom scattering from the heat absorption body 11 to the support body 12.

However, when the gap between the heat absorption body 11 and thesupport body 12 is too wide, since the heat medium 11 can easily passthrough the space between the heat absorption body 11 and the supportbody 12, it becomes difficult for the heat medium to pass through theflow paths 13 b formed in the honeycomb unit 13, and the transferringefficiency of heat to the heat medium 11 decreases. Therefore, the gapbetween the heat absorption body 11 and the support body is desirablyset to a predetermined gap with which a heat insulating effect isgenerated.

Therefore, the area proportion of the heat insulating region ispreferably 5% to 50%.

Hereinafter, the actions and effects of the thermal receiver of theembodiment will be listed.

The embodiment does not only exhibit the actions and effects of (1), (3)and (4) of the first embodiment, but also exhibits the following effect.

(6) In the thermal receiver of the embodiment, the air layer is presentbetween the heat absorption body and the support body, and, when theheat medium is suctioned, the air layer portion between the heatabsorption body and the support body is also suctioned, therebygenerating the flow of a predetermined flow amount of the heat medium.Therefore, the layer of the flowing heat medium functions as aheat-retention layer (heat insulating layer), and it is possible toeffectively prevent heat from scattering from the heat absorption bodyto the support body.

Fourth Embodiment

Hereinafter, a fourth embodiment, which is an embodiment of the solarthermal power generation device of the invention, will be described.

In the solar thermal power generation device according to theembodiment, the thermal receiver according to the first embodiment ofthe invention is used.

FIG. 5A is a front view schematically illustrating a receiver array thatconfigures the solar thermal power generation device according to theembodiment of the invention, and FIG. 5B is a cross-sectional view ofthe receiver array cut along the line C-C illustrated in FIG. 5A.

FIG. 6 is an explanatory view schematically illustrating the solarthermal power generation apparatus according to the embodiment of theinvention.

In a receiver array 20 illustrated in FIGS. 5A and 5B, multiple thermalreceivers 10 are disposed in a box-like frame 22, in which a solar lightirradiation surface is opened, in a state in which the surfaces of theheat absorption bodies 11 which receive the radiation of solar light arearrayed to face the front. In the present specification, an assembly ofmultiple arrayed thermal receivers will also be referred to as areceiver array.

That is, gas exits 12 b for the support body 12 that configure thethermal receiver 10 are coupled with a bottom portion 22 a of the frame22, and the bottom portion 22 a forms a closed space except a portionthat is connected to a pipe 22 b. Therefore, the heat medium 14, such asthe air, passes through the flow paths 13 b formed in the honeycomb unit13, is heated using the heat absorption body 11, and then collected in aspace formed in the bottom portion 22 a of the frame 22 through theexits 12 b for the heat medium in the support body 12. After that, theheat medium 14 is led to a vapor generating device 33, described below,through the pipe 22 b.

In actual cases, the pipe 22 b, a container coupled with the pipe 22 b,or the like is coupled with an apparatus that suctions gas, such as anefflux pump. Therefore, when the efflux pump or the like is driven, theheat medium 14, such as the air, around the thermal receiver 10 passesthrough the flow paths 13 b formed in the honeycomb unit 13, and heatstored in the heat absorption body 11 is transferred to the heat medium,such as the air.

In FIGS. 5A and 5B, the air around the thermal receiver 10 is led to theflow paths 13 b in the honeycomb unit 13, the solar thermal powergeneration device may have a dual structure having two rooms as thebottom portion 22 a of the frame 22. In this case, suddenly, the heatmedium 14, such as the air, does not flow into the flow paths 13 bformed in the honeycomb unit 13, but flows into one of the two rooms,thereby flowing into spaces 22 c present between the multiple thermalreceivers 10. After that, the heat medium 14 is blown out from the voidformed in the enlarged portion 12 a, and immediately flows into the flowpaths 13 b formed in the honeycomb unit 13 of the thermal receiver 10.

In this case, since the heat medium 14 exchanges heat with the supportbody 12 having an increased temperature for the first time, the thermalefficiency becomes large.

As illustrated in FIG. 6, in the solar thermal power generation device30 of the embodiment of the invention, the receiver array 20 is disposedat the height location of a central tower 32, and the vapor generationdevice 33, a heat storing device 34, a vapor turbine 35 and a coolingdevice 36 are sequentially disposed below the receiver array. Inaddition, multiple heliostats 37 are disposed around the central tower32, the heliostats 37 are set so that the reflection angle or therotating direction using the vertical direction as the axis can befreely controlled, whereby the solar thermal power generation device isautomatically controlled so that momentarily changing solar light isreflected at the heliostats 37 and collected at the receiver array 20 inthe central tower 32.

The vapor generating device 33 is a division that generates vapor fordriving the vapor turbine 35. In the vapor generating device 33, theheat medium 14 heated using the heat absorption body 11 in the receiverarray 20 passes through the pipe 22 b, then, is led to the pipe in thevapor generating device 33 (boiler), and the heat exchange with the heatmedium 14 occurs. Water heated through the heat exchange generates watervapor.

The generated water vapor is introduced into the vapor turbine 35,drives and rotates the vapor turbine 35, and a power generator is driventhrough the rotation of the vapor turbine 35, thereby generatingelectricity.

The heat storing device 34 is a portion that temporarily stores the heatobtained using the heat medium 14, and sand is used as a heat storingmember. In the heat storing device 34, a heat storing pipe (not shown)connected to the pipe 22 b is made to pass through the sand, and theheat medium 14 heated using the heat absorption body 11 is made to passthrough the heat storing pipe, thereby supplying heat to the sand, whichis a heat storing material. Since the heat storing material has a largethermal capacity, the material can absorb and store a large amount ofheat. Meanwhile, the heat storing material accommodated in the heatstoring device 34 is not limited to the sand, and may be anotherinorganic material having a large thermal capacity, and may be a varietyof salts and the like.

Another vapor generating pipe (not shown), separately from the heatstoring pipe, is made to pass through the sand in the heat storingdevice 34, a non-heated heat medium is made to flow through the vaporgenerating pipe at times during which solar light cannot be used, suchas at night, and the heat medium is heated using the sand of the heatstoring material having an increased temperature. The heat storing pipemay function as the vapor generating pipe.

The heated heat medium flows into the vapor generating device 33 so asto generate water vapor, and, as described above, electricity isgenerated through the driving of the vapor turbine 35.

The water vapor that has passed through the vapor turbine 35 is led tothe cooling device 36, is cooled in the cooling device 36 so as to turninto water, undergoes a predetermined treatment, and then returns to thevapor generating device 33.

The cooling device 36 is preferably configured so that the heat medium14, which has been made to pass through the vapor generating device 33so as to be cooled, passes through a cooling pipe (not shown) in thecooling device 36. Since the heat medium 14 is made to pass through thecooling pipe so as to be heated, it is possible to efficiently use theheat absorbed at the thermal receiver 10.

In addition, as described above, when the pipe is configured so that theheat medium 14 that has collected heat flows into spaces 22 c formedbetween the multiple thermal receivers 10 in the receiver array 20,furthermore, it is also possible to effectively use the heat of thesupport body 12 in the thermal receiver 10.

Hereinafter, the actions and effects of the solar thermal powergeneration device of the fourth embodiment of the invention will belisted.

(1) In the solar thermal power generation device of the embodiment,since the thermal receiver according to the first embodiment is used, itis possible to efficiently convert the radiated solar light into heat,and to efficiently generate power.

(2) In the solar thermal power generation device of the embodiment,since the receiver array has multiple thermal receivers, it is possibleto use a large amount of solar heat, and to carry out a large amount ofpower generation.

(3) In the solar thermal power generation device of the embodiment,since the heat storing device is used, and heat generated using solarlight can be stored in the heat storing device, it is possible togenerate power even at night or rainy days, during which there is nosolar light.

Other Embodiments of the Invention

Hereinafter, other embodiments of the thermal receiver of the inventionwill be described.

The honeycomb unit 13 (heat absorption body 11) is configured of theporous silicon carbide having open pores in the first embodiment of theinvention, and is configured of the porous silicon carbide having openpores and the silicon 15 that fills up the open pores in the poroussilicon carbide in the second embodiment. However, the thermal receiverof the invention is not limited to the above configurations, and, forexample, the honeycomb unit 13 may be configured of dense siliconcarbide having a small porosity.

In a case in which the honeycomb unit 13 is configured of dense siliconcarbide, since the thermal capacity of the honeycomb unit 13 becomeslarge, the heat storing performance is excellent. In addition, asdescribed above, since silicon carbide is stable in the air even at1600° C., and is extremely excellent in terms of thermal resistance, theperformances do not change even in long-term use. In addition, sincesilicon carbide has a high thermal conductivity, it is possible totransfer the heat stored in the honeycomb unit 13 to the heat medium.

In a case in which the honeycomb unit 13 is configured of dense siliconcarbide, the porosity is preferably 5% or less.

In the honeycomb unit 13 (heat absorption body 11) configured of densesilicon carbide, regarding the flow paths in the honeycomb unit 13, whena vertical cross-section is formed with respect to the flow paths,similarly to the case of the first embodiment, the number of the flowpaths per square meter is desirably 31.0 paths/cm² to 93.0 paths/cm².

Regarding the thickness of the wall portion in the honeycomb unit 13,similarly to the case of the first embodiment, the thickness of the wallportion between the flow paths is preferably 0.1 mm to 0.5 mm.

In a case in which the heat absorption body 11 is manufactured usingmultiple honeycomb units made of dense silicon carbide, the heatabsorption body can be manufactured by adhering the honeycomb unitsusing the adhesive paste including at least one of the inorganicparticles, the inorganic fiber and the inorganic binder, which aredescribed in the first embodiment, or by adhering the honeycomb unitsusing silicon which is described in the second embodiment.

In addition, in the thermal receiver according to other embodiments ofthe invention, an inorganic heat insulating member may be interposedbetween the heat absorption body and the support body.

Examples of the inorganic heat insulating member include the memberobtained using the adhesive paste used as an adhesive that adheres andbinds multiple honeycomb units in the second embodiment. That is, inthis case, the adhesive paste is coated around the heat absorption bodyformed by joining multiple honeycomb units, and the heat absorption bodyis adhered to the support body through the coated layer.

The adhesive paste includes at least one of the inorganic particles, theinorganic fiber and the inorganic binder, and may include an organicbinder. Since the adhesive paste has been described in the secondembodiment, the adhesive paste will not be described in detail herein.

In the embodiment, the thermal receiver made of multiple honeycomb unitshas been described, but the thermal receiver of the embodiment of theinvention may be configured of one honeycomb unit

When used in the solar thermal power generation device 30, since theheat absorption body 11 reaches approximately 1000° C., moisture and thelike in the adhesive layer are volatilized, and an inorganic heatinsulating member, in which the inorganic particles and the inorganicfiber are coupled using the solid content of the inorganic binder, isformed. Meanwhile, in a case in which the adhesive layer includes anorganic binder, it is needless to say that the organic binder isdecomposed and eliminated.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A thermal receiver comprising: a heat absorption body made of atleast one honeycomb unit having a plurality of flow paths arranged forcirculation of a heat medium; a support body which supports the heatabsorption body and which allows circulation of the heat medium; and theheat absorption body including silicon carbide and being supported at aposition away from an inner surface of the support body by apredetermined distance.
 2. The thermal receiver according to claim 1,wherein a holding material including an inorganic fiber is interposedbetween the heat absorption body and the support body.
 3. The thermalreceiver according to claim 1, wherein the heat absorption body issupported by fixing members provided in the support body, and an airlayer is present between the heat absorption body and the support bodyexcluding the fixing members.
 4. The thermal receiver according to claim1, wherein an inorganic heat insulating member is interposed between theheat absorption body and the support body.
 5. The thermal receiveraccording to claim 2, wherein the holding material is made of analumina-silica fiber, an alumina fiber or a silica fiber.
 6. The thermalreceiver according to claim 5, wherein a composition ratio of alumina tosilica (alumina/silica) is from 60/40 to 80/20.
 7. The thermal receiveraccording to claim 1, wherein, when a cross-sectional area of the heatabsorption body in a plane parallel to a surface of the heat absorptionbody, to which solar light is radiated, is indicated by A, and anopening area of the support body including the plane is indicated by B,an area proportion of a heat insulating region, which is represented bya following formula (1), is 5% to 50%,Area proportion of a heat insulating region (%)=(B−A)×100/B  (1).
 8. Thethermal receiver according to claim 1, wherein the heat absorption bodyis made of porous silicon carbide.
 9. The thermal receiver according toclaim 1, wherein the heat absorption body includes porous siliconcarbide, and silicon that fills up pores in the porous silicon carbide.10. The thermal receiver according to claim 8, wherein porosity of theporous silicon carbide is 35% to 60%, and an average pore diameter is 5μm to 30 μm.
 11. The thermal receiver according to claim 1, wherein theheat absorption body is made of dense silica carbide.
 12. The thermalreceiver according to claim 1, wherein the plurality of flow paths areprovided in the heat absorption body at 31.0 paths/cm² to 93.0paths/cm², and a thickness of a wall portion between each of theplurality of flow paths in the heat absorption body is 0.1 mm to 0.5 mm.13. A solar thermal power generation device comprising the thermalreceiver according to claim 1.